No deleterious variants of human TSLP or CRLF2 have been reported (3), but we previously identified 3 patients with AR IL-7 deficiency (29), prompting further investigation into the role of IL-7 in T cell development and human immunity through an in-depth analysis of these 3 patients, including the screening of our database of over 23,000 exomes for additional patients carrying rare predicted deleterious biallelic variants of IL7. Here, IL7 is linked to hyperinsulinemic hypoglycemia, familial, 4.